Took one recently. They can vary in difficulty in my opinion.
This one had basic numerical reasoning (google that phrase for examples).
A test on your command of the written language.
Abstract Reasoning, this is where you look at shapes and choose the odd one out, or next shape. can be tricky sometimes depending on your ability.
The final step is to analyse your personality. Are you a team worker, introvert/extrovert? How do you react under stress etc. Answer them truthfully as they are designed to catch you out if you attempt to fit it to the job description.
After you've sat it, ask for a copy. It makes for interesting reading and you're entitled to the results.