Let us simplify that a bit. A covenant is simply something demanding that you do, or don't do something.It is found in deeds for the sale of land and controls the new owner. It will be repeated when the land is registered with the Land Registry.
And it normally controls the activity of every successive buyer; they are bound by it; unless what it demands is completely impossible for them to perform.
What does this clause say?
Some covenants are not enforceable unless the seller retains an affected interest personal to himself. For example my family sold land for houses with covenants that no shed was to be in the garden without permission; well, I could, in theory, object because I retain adjacent land and am 'affected', and a succession of careful solicitors have asked me whether the shed of the house their client is buying had my or my predecessor's permission. My feeling is that if I didn't own land next door, they really needn't ask, because I could not be 'affected' (This, I think was the first reason for Leicester Square gardens still existing; the seller retained an affected interest) Different considerations apply when an estate has covenants in the interest of al the householders or flat owners.