If you type ps aux, you’ll get a detailed output of all linux processes running at that time.
Here’s a little trick that allows you to sort that output by memory consumption, so the biggest memory consumers are at the bottom.
$ ps aux | sort -nk +4 | tail -n 10
This sorts the output of ps by the 4th field (%MEM) and only shows the last 10 lines.
Alternatively, you can also pass the --sort parameter to ps directly. For instance:
$ ps aux --sort -rss | head
This shows the top consumers at the top.