Other forms: longer-lasting
Long-lasting things stick around for a while. If the medicine you're taking for your sore throat has long-lasting side effects, they'll affect you for many weeks or even months.
A long-lasting relationship lasts for years, and long-lasting makeup stays on your face all day, until you wash it off at night. This adjective can mean that something is durable or resilient, or in other words that it holds up over time. Other things are simply long-lasting by coincidence — they've just been there for a long time.