Computer specs are detailed information about how your computer runs and the hardware / software that makes it run. When people want a computer, they look at the specs to determine how good the computer is and if it's the right computer for them.
Computer specs can be listed as very basic:
RAM amount, HDD space, CPU speed (in GHz, as of today) and that's pretty much about it.
This is what people mainly look for the most because these 3 things matter the most.
Or they can be listed with lots of information that only a "techy" would understand. These things can be:
GPU: type, memory, speed, cache, manufacturer
CPU: speed, cores
RAM: type, size, frequency
Motherboard: manufacturer, compatibility, PCI slots, RAM slots, etc.
To check what your specs are you can visit the link below. It'll show you how to check your specs for Windows, Linux and Mac.
You can also use this program to get (almost) every detail about your computer.