Adjectives - words which describe a noun - like 'big', 'red', 'cheap' - have different endings depending on the gender of the noun, the case and whether the noun is singular or plural
The following table is from Adam Ĺukasiak's Clozemaster site. I'm just putting a copy here in case something happens to that site!
You might want to give Clozemaster a whirl. The basic version is free and a great way to practice your Polish.
And if you would like to know more about Polish Adjective Endings because you're a bit of a Grammar fan the correct search term for Google is "Polish Adjective Declensions".
Table explantion is below
If you aren't clear on your cases yet see the Polish Language Cases - Which case to use and when page.
Plural Masculine Personal refers to masculine nouns that are male people or animals like "men", "boys", "cats", etc.