I am no chemist too, but I think I can give you answer to your questions.
As you can see, the word "indolol" are derived from "indole"(aromatic structure, the core structure of all tryptamines) and -ol, the suffix for alcohols. And an alcohol is "any organic compound in which a hydroxyl functional group (-OH) is bound to a carbon atom, usually connected to other carbon or hydrogen atoms." I copied this definition from wikipedia. So, technically, 4-HO-DET is an alcohol. The next interesting thing, alcohols can form esters with oxygen-containing acids.
Look at the acetic acid, for example:
and at the 4-HO-DET(aka ethocin, named after psilocin - 4-HO-DMT):
and finally at the resulting ester 4-AcO-DET:
It is also called Ethacetin(after 4-AcO-DMT, which is Psilacetin).
And also, phosphate ester exists, 4-PO-DET(aka Ethocybin, named after psilocybin - phosphate ester of psilocin):
Look at the corresponding acid - phosphoric acid:
As you probably know, there is the hypothesis: both 4-PO-DET and 4-AcO-DMT are metabolized(by dephosphorylation and deacetylation) in 4-HO-DET. Some people may disagree, but all three compounds should produce approximately the same range of effects, although 4-HO-DET should be most potent by weight.