Apple hardware terms, in plain English.

A UDID (Unique Device Identifier) is a 40-character hexadecimal string that uniquely identified every iOS device. In the early days of the App Store, any installed app could read it — which made it convenient for developers and, for the same reason, a privacy problem: one persistent identifier that could be shared across apps to track a single device.

Apple deprecated UDID access and, since May 1, 2013, rejects app submissions that read it. Modern iOS gives each app a per-app vendor identifier instead, so two apps on the same device see different values.

The model identifier is the machine-readable hardware ID the operating system reports — a string like iPhone17,3 or iPhone18,2. One identifier maps to exactly one hardware product; it is what diagnostics logs, development tools, and analytics data speak when they name a device.

It is distinct from the A-number (such as A3258), which marks the regulatory and regional variant, and from the part-style model number (such as MN572LL/A), which encodes region, storage, and color for sales and parts. The marketing name — "iPhone 17" — covers all of those variants at once, which is exactly why the identifier is the one to quote for support, parts, and resale.

A SoC (system on a chip) is a single package that integrates the CPU, GPU, memory controller, and other subsystems. Every iPhone runs an Apple-designed A-series SoC; modern Macs run Apple silicon M-series chips. The SoC model answers "how fast is this device" far better than core counts or clock speeds alone, because it fixes the whole performance profile.

Software requirements are often expressed in SoC terms: an app that requires "Apple M1 or later" is gating on the chip generation, not the model name of the Mac.

The baseband is the modem subsystem — a processor separate from the SoC that handles the cellular radio: registering on the network, managing bands, and carrying data and calls. Its firmware version can matter when you are troubleshooting cellular behavior or checking band support before travel or resale.

Wi-Fi and Bluetooth live on their own radios; "baseband" specifically means the cellular side.

A battery cycle is a full discharge of 100% of battery capacity, accumulated across charges — use 75% today, recharge fully, use 25% tomorrow, and you have completed one cycle. The cycle count is the running total: it is the honest measure of how much work a battery has done, the way mileage reads on a car.

Apple designs current iPhone batteries to retain up to 80% of original capacity after about 1,000 complete cycles (older models were rated for 500). But since iOS 10, the cycle count is not exposed to apps — it appears only in the system's own analytics and diagnostics data, so no App Store app can display it on a current iPhone.

Thermal state is the operating system's own verdict on how hot the device is running — nominal, or one of several levels of thermal stress. When a device heats up, iOS scales back performance to protect the hardware, so sustained thermal pressure is one of the fastest ways to turn a fast phone into a slow one.

Because heat and battery wear go together, thermal state is usually more diagnostic than a single battery percentage: a device that is consistently hot while idle is telling you something regardless of what any health screen says.

The hardware tree is the nested inventory of controllers, interfaces, and components the operating system enumerates from boot: chipset and memory context, storage, internal buses, USB details, radios, and which sensors are actually present. It is the closest thing a device has to a parts list of itself.

Two phones with the same marketing name can differ in the tree — a regional variant with different radios, a repaired unit with a different part — which is why reading the tree beats quoting a spec sheet.

NAND flash is the non-volatile memory that stores everything on the device — the silicon behind "256 GB" on the box. It is separate from RAM, which is volatile working memory that empties at every restart. For most hardware questions, what matters about NAND is capacity, how much is free, and how fast it is.

A nearly full NAND can slow a device down well before any health screen flags a problem, which is why free space is worth checking during intake or before a resale grade.

A benchmark runs a standardized workload and reports a score, so you can compare devices against each other — or one device against its own past state. Benchmarks are relative measures, not absolute truth: they are sensitive to thermal state, charge level, and background activity, which is also what makes them useful for spotting a throttled or degraded device.

On Apple hardware, benchmark results map cleanly across SoC generations, which is why identification and performance testing naturally go together.