'against' is a preposition meaning: 1. in opposition to; contrary to; adverse or hostile to: twenty votes against ten; against reason. 2. in resistance to or defense from: protection against burglars. 3. in an opposite direction to: to ride against the wind. 4. into contact or collision with; toward; upon: The rain beat against the window. 5. in contact with: to lean against the wall. 'in front of' is also a preposition, meaning 'in direct view of' Examples:    My car is parked in front of your house.    I'll be waiting in front of the restaurant.     'in front of' also means 'before' Examples: - before an audience - before his eyes - before the court - before the judge - head - in public, orchestra pit

'Against ' has other meanings as well, but in the sense you are referring to, it means 'in physical contact with.' A bicycle could lean against a house. I can lean against the front of the house, but it can also lean against the side of the house or lean against the back of the house. If the bicycle is in front of the house, it might be leaning against the front of the house. It might also be in front of the house, but not against the house. 'The bicycle is in the street in front of the house."