What is RAM?
There are typically two types of memory on a computer. There is long term memory, such as a hard drive or SSD, and then there is RAM. RAM stands for Random Access Memory and the computer can use it to quickly look up information that it needs. It is much quicker than regular long term memory, but it can also not save any data unless the power on the computer is on. Without an adequate amount of RAM your computer will feel slow and sluggish. Upgrading the RAM in an old laptop can often breathe new life and enable you to keep it for quite a while longer.
How is RAM faster?
One reason a hard drive is slower than RAM is that it is mechanical. It has a disk that has to spin in order to access the correct location, you might have heard the spinning sound from your own computer. RAM on the other hand has no moving parts and can therefore access data faster.
One reason that an SSD (Solid state drive) is also faster than a regular hard drive is that it also has no moving parts. That is also why an SSD is quiet. And SSD is still long term storage so reading and writing to the disk takes longer than for RAM which is short term storage, meaning when there is no power it can’t be saved.
A second reason RAM is faster is that it sits closer to the CPU. The CPU reads data from RAM memory, and if something is missing then it is loaded from main memory into RAM so that the CPU can read it.
Types of RAM
There are many different kinds of RAM in use today. Some of them are static RAM, dynamic RAM, Synchronous Dynamic RAM, single data rate Synchronous Dynamic RAM, double data rate Synchronous Dynamic RAM (DDRX), and graphics data rate Synchronous Dynamic RAM (GDDRX).
You will often find DDRX and GDDRX in computers today, where X is usually a number representing the generation of the ram.
When looking for ram you typically want to look for DDR4 ram which is the newest generation of double data rate Synchronous Dynamic RAM. For GDDR ram you should be looking for generation 5 or 6.
In most laptops these days you will see either DDR3 or DDR4 RAM. Although DDR3 is slower and uses more power it is still a popular options. Older parts also tend to be a bit cheaper so often it can be used to lower the cost of the laptop. Manufacturers often have to compromise on some things, and you probably wont notice much difference regardless of which kind you have as long as you have enough. If you do resrouce heavy tasks on the other hand then that might be a different story.
How much RAM can a computer have?
The amount of RAM that a computer can have varies. Servers can have hundreds of GBs of ram and laptops can also have a large amount, sometimes over 100GB. Typically though you will mostly find laptops that have 8-16GB, sometimes 32GB.
How much RAM do you need?
If you are to buy a computer today I would recommend a minimum of 8GB. Many computers come with 16GB and that is probably the better option if there is not a significant price difference. You should make sure that you also have the option of adding more memory, at least up to 32GB, so that you can upgrade your computer in the future if you want to keep it for a long time.
If you want some examples on how much ram good laptops have you can check out the post on best laptop for law school. In that post there are several good laptops, including options with both DDR3 and DDR4.