A bilateral agreement is an agreement undertaken between two parties.
Bilateral agreements are commonly found between states that do not prescribe to an agreement reached between other groups of states.
For example, the USA is attempting to reach a series of bilateral agreements with individual states which will exempt its citizens from prosecution by the International Criminal Court.
In areas which fall within their competence, EU member states can conclude bilateral agreements with third countries.
Links - see also
Bilateral Agreements Switzerland - EU, Agreements with other countries and Mixed agreement.