What is the main difference between the formal and informal qualifications for the house of represenatives

The main difference between formal and informal qualifications for the House of Representatives are that:
Formal qualifications belong to someone's age, nationality or working class while the informal qualifications are related to someone's individual qualities or ability of getting vote for example a person belongs to which party or how much his/her name is familiar to the general public, his ethnic background/Gender etc, all of the factors which count when he needs to get votes...