The difference between a tenant and a lodger is that a lodge is someone who lives in the house with the tenant and is renting out a room in the house.
A tenant is someone who lives in someone's house but is renting the house for themselves or their family and has their name on the rental lease agreement.
The tenant pays rent to a landlord who lives in another house.
The lodger is the person that lives in a room in the same house that the tenant lives in.
The lodge also pays rent but pays rent to the person who owns the house but both live in the same house.
So if you rent out a room in someone's house to live in you're considered to be a lodger and not really a tenant who rents out the entire house.