Digestion of protein

[alFReDNSH]

I'm a little bit researching about digestion of protein but I'm confused. I'm in high school and I just want to understand these things:

1. What are the exactly stages of digestion of protein?
2. What are the differences between hydrochloric acid, trypsin, pepsin and other enzymes that has effects on protein and amino acids in the digestion?
3. What are the difference between peptides, polypeptides, amino acids and other units of protein?

If here is not the right place to ask these questions, please if you know the right place, write it.

Thank you in advance

[JackBean]

Well, amino acids are the basic building blocks connected by peptide bonds and forming peptides, these are divied by number of AAs to dipeptides, tripeptides etc. or oligopeptides (usually 2 - 10 AAs), polypetides (up to 100 AAs or ~ 10 kDa or something like that) and proteins (even larger).

So, the peptides (and proteins) are digested by braeking the peptide bonds either by acid catalytic (HCl) or enzymatically (pepsin, trypsin etc.). These enzymes have different specificity (usually hydrolizing after some AA like basic amino acids as Arg and Lys (trypsin) or after hydrophobic amino acids (I think chymotrypsin)) or can differ in the way they do it.