As a regular user of the forums I have not noted much use of Tags,
Tags are a filter mechanism. I envisage their primary use is in Income and category reports to filter a subset of transactions.
An example may be expenditure on a holiday, so you are likely to have fuel, rent, food etc. These appear in your Income and expense reports but there is no way to just see holiday expenses, using a tag of say Hol2020 and assigned this to each transaction then in the I & E report setting a filter tag of Hol2020 will only show these transactions.
Like the others, I have used tags so as to get a true idea of expenditure say of (hopefully) a non recurring event. In this case my daughters wedding last year! Phew, still not fully recovered financially.
The hardest thing to do with Tags is to delete them. You use the Extension Find & Replace to do it, but as I need to delete them so infrequently I can never quite remember the procedure.
If you want to experiment with tags I would suggest you create a new Test File & have a play so as to make sure you are conversant with both adding & removing them.