EMZETT.Components
In short: The individual physical parts of a computer — e.g. CPU, RAM, motherboard, power supply, storage, graphics card — which together form the overall system.
In more detail: The modular design made up of interchangeable components (especially with desktop PCs) allows targeted upgrades of individual parts instead of a complete new purchase. Compatibility between components (socket, form factor, ports) is the central constraint here.
In Depth
The motherboard’s role as the connecting piece
The interplay of components follows a clear hierarchy: the motherboard forms the central connecting piece, to which all other components are connected via standardised interfaces — the CPU via the CPU socket, RAM via RAM slots, mass storage via SATA/NVMe, graphics cards and other expansion cards via PCIe slots. This standardisation is the reason components from different manufacturers can be freely combined, as long as the respective interfaces match — a RAM module from manufacturer A works fine with a motherboard from manufacturer B, as long as both support the same memory type (e.g. DDR5).
Compatibility as the central bottleneck
Compatibility is the central bottleneck when putting together a system: a CPU has to match the motherboard’s socket, RAM the supported memory type and the motherboard’s maximum clock rate, the power supply has to deliver enough power for all installed components (especially relevant for power-hungry graphics cards, which in extreme cases need several hundred watts alone), and the case has to be physically large enough for all chosen parts — in particular, a graphics card’s length and a CPU cooler’s height are common pitfalls when a compact case is chosen. This interdependence is a main reason building your own desktop PC requires careful planning — unlike a pre-configured system, where the manufacturer has already checked this compatibility.
The bottleneck principle
An important practical concept when putting components together is so-called bottlenecking: the overall performance of a system is always limited by the slowest participating component, regardless of how powerful all the other parts are. An extremely powerful graphics card combined with a weak CPU can’t unleash its full potential in many games, because the CPU can’t compute new frame information and deliver it to the graphics card fast enough — a balanced ratio between the core components is therefore often more important than isolatedly maximising a single component.
Modularity as an upgrade strategy
The modular design allows targeted partial upgrades over a system’s lifetime: a user can start with a moderate configuration and later specifically replace the component promising the biggest performance gain (often RAM or mass storage first, since these are comparatively cheap), instead of replacing the entire system at once. This option barely exists any more with laptops and especially smartphones, since more and more components there are permanently soldered instead of socketed, for space and cost reasons.
See also: Desktop PCs, Motherboard/Mainboard