When apostrophe's required.

I understand that I Like most people, often use an apostrophe when I should not but don't fully understand when that is.
I was reading about how if it is a name you use an apostrophe to make it possessive but for other words you shouldn't but to be honest I don't know what the details are.
The two common uses for an apostrophe I know of and think I understand are as follows. "Bernie's garbage." Could be correct both if it is a contradiction of, "Bernie is" or to indicate possession.
Therefore that sentence needs more context.
Better sentences would contain more information such as, "Everyone thinks Bernie's garbage because he stole the name he uses here and hangs around playgrounds." Or. "That old condom wrapper is probably Bernie's garbage, it's the brand he uses and most people wouldn't have left it in a playground."
Let's see those opinions. Should be a great discussion.
I was reading about how if it is a name you use an apostrophe to make it possessive but for other words you shouldn't but to be honest I don't know what the details are.
The two common uses for an apostrophe I know of and think I understand are as follows. "Bernie's garbage." Could be correct both if it is a contradiction of, "Bernie is" or to indicate possession.
Therefore that sentence needs more context.
Better sentences would contain more information such as, "Everyone thinks Bernie's garbage because he stole the name he uses here and hangs around playgrounds." Or. "That old condom wrapper is probably Bernie's garbage, it's the brand he uses and most people wouldn't have left it in a playground."
Let's see those opinions. Should be a great discussion.