Grammar, explained plainly

Americans say 'I could care less' but shouldn't it be 'I couldn't care less'? → I used 'actually' and my colleagues seemed confused - what does it really mean? → My teacher said 'eventually' doesn't mean what I think - what's the difference? → What does 'sensible' mean in English? It doesn't seem to mean what I expected. → When do you use 'make' and when do you use 'do' in English? I always confuse them. → What is the difference between 'say' and 'tell' in English? → What is the difference between 'lend' and 'borrow'? I always confuse them. → What is the difference between 'bring' and 'take'? → When do you use 'since' and when do you use 'for' with the present perfect? → What is the difference between 'used to', 'be used to', and 'get used to'? → What's the difference between 'affect' and 'effect'? → What's the difference between 'its' and 'it's'? → What's the difference between 'there', 'their', and 'they're'? → When do you use 'less' and when do you use 'fewer'? → When do you use 'who' and when do you use 'whom'? → Why do people write 'could of' instead of 'could have'? → What's the difference between 'boring' and 'bored'? → What's the difference between 'lie' and 'lay'? → What's the difference between 'your' and 'you're'? → What's the difference between 'hear' and 'listen'? → What's the difference between 'see', 'look at', and 'watch'? → What's the difference between 'speak' and 'talk'? → What's the difference between 'hard' and 'difficult'? → When do I use the present perfect tense in English? → What's the difference between 'may' and 'might'? → What's the difference between 'despite' and 'although'? → What's the difference between 'unless' and 'if not'? → What's the difference between 'I wish' and 'I hope'? → When do I use 'so' and when do I use 'such'? → What's the difference between 'too' and 'very'? → When do I use 'either/or' vs 'neither/nor'? → What's the difference between 'by' and 'until'? → What's the difference between 'during' and 'for' with time? → What's the difference between 'already', 'yet', and 'still'? → When do I use the present simple vs the present continuous? → What's the difference between the past simple and past continuous? → What's the difference between 'will' and 'going to' for the future? → What's the difference between 'should' and 'ought to'? → When do I use 'much' and when do I use 'many'? → What's the difference between 'few' and 'a few'? →