The Spanish Civil Code holds a classification of contracts:
Consensual and Real Contracts
Bilateral (Synallagmatic) Contracts
Gratuitous and Onerous Contracts, Onerous subdivided in: commutative and Aleatory contracts.
Nominate and Innominate Contracts
Instantaneous, long-term and on Instalment Contracts
These distinctions can have important practical consequences when non-performance or breach of contract arrises.
Do you know what your position holds in a contract?
A good advice can save you worries later on