First decide on the platform you wish to use:
Software - Apple iOS, Microsoft Windows, Android, Chromebook, Linux
Hardware – desktop, laptop, all-in-one, or tablet
Second decide on hardware brand – Apple, HP, Dell, Acer, Asus, Lenovo, or ????
For many doing email and occasional internet searches, a tablet is sufficient for an hour here or there. A more intensive usage (10+ hours a week) might require higher performance hardware. If you are just surfing the internet or streaming video, most products with enough memory and a SSD (Solid State Drive) will provide adequate performance.
The central processing unit (CPU) is the engine of the computer. The lower end CPUs like Intel Pentium or AMD E1 score in the hundreds on benchmark tests and have performance on par with tablets - https://www.cpubenchmark.net/.
The mid-range CPUs like Intel i3 or AMD Phenom II score in the low thousands.
The higher CPUs like Intel i7 or AMD Ryzen 7 score 15,000+. You want performance, this is it.
To support the CPU, the random access memory (RAM) should be at least 4GB, preferably 8 GB.
The storage device is transitioning from mechanical hard drive (HD) to solid state drive (SSD). The SSD is faster than the HD so if you want performance, the SSD device is preferred.
It’s recommended to shop on-line or in a store to see what fits your needs. If you are not rushed, watch for specials.