A company that raises money by selling bonds often does so in several pieces at the same time. Each piece is a tranche, and each has its own terms, most commonly a different maturity. A single deal might include a bond due in 3 years, another due in 10 years and a third due in 30 years, each priced at a different interest rate.
Splitting the deal lets the issuer match different investors' wishes. Some buyers want short debt and others want long, and the issuer can spread out when its debt comes due so that not all of it must be repaid or refinanced at once.
In structured finance, such as securitizations, the word has a sharper meaning. The tranches are ranked, with senior ones paid first and junior ones absorbing losses first, and they carry different ratings and yields.
Look at the size, maturity, rate and ranking of each tranche, and work out when the company will need to repay or refinance each of them.