what is

[dee_jas]

In betting terms, what is a propostition bet.

[Dunder]

Really it can be any bet that is not a regular money line, spread or total.
An example would be, Will there be overtime?

Since you are European, pretty much all bets available in a soccer match (first goalscorer, correct score, half-time-full-time etc.) would all be considered as proposition bets albeit the US facing books tend to offer two-way outcomes

e.g.
Will Messi score in the match: Yes +100, No -120

Proposition bets tend to be less efficient than spreads/totals etc and despite the higher juice, many 'sharps' use them.

[dee_jas]

Really it can be any bet that is not a regular money line, spread or total.
An example would be, Will there be overtime?

Since you are European, pretty much all bets available in a soccer match (first goalscorer, correct score, half-time-full-time etc.) would all be considered as proposition bets albeit the US facing books tend to offer two-way outcomes

e.g.
Will Messi score in the match: Yes +100, No -120

Proposition bets tend to be less efficient than spreads/totals etc and despite the higher juice, many 'sharps' use them.

Thanks Dunder