[a1a]

Let's try this one again, from the start:

It's sexism if a human being[1] is being mistreated, harassed, or "labeled" because of their gender[2].

It's perhaps easier to understand from analogy[3], take a look at racism[4] and see if you can find any similarities.

Feel free to ask any question if something is still unclear.

[1] https://simple.wikipedia.org/wiki/Human_being

[2] https://simple.wikipedia.org/wiki/Gender

[3] https://simple.wikipedia.org/wiki/Analogy

[4] https://simple.wikipedia.org/wiki/Racism