Government entitlement programs are those programs where people are entitled by law to a certain level of benefits so long as they fit the criteria for the program. The government must pay these benefits regardless of how much money is available.
Not all government programs are entitlements. Some programs will give benefits to people, but only until their budget runs out. Or they might, due to budgetary concerns, give benefits to only some of the people who qualify.
Entitlements are those programs like Medicare and Social Security that must pay out the promised benefits to everyone who qualifies unless Congress changes the law. Until then, all benefits must be paid and the government must find the money to do so, regardless of the impact on the government’s finances.