Sometimes? For some people?
Jealousy is a big word, and in our culture it is used to cover a bunch of not really closely related things. Jealousy is used to cover insecurity and envy, for instance.
If what you are actually dealing with is insecurity, work on the relationship so that you feel more secure. Sometimes this means asking for reassurance from your partner that they are still into you. Sometimes asking for more specific attention or time helps. Figure out what would reassure YOU and talk with your partner. It is ok to ask for what you need. You may or may not get it, but, figure out what you need and communicate.
If what you are feeling is envy, then, again, try asking. Envy is usually someone else getting to do something that you want to do too. My partner takes his wife out to dinner to a place that I have been dying to go to with him....or usually, actually, me getting to go somewhere that she wants to go to. This is fixable, but, you need to figure out what you want and ask.
Also....if your partner is out with someone that isn't you.....find something to do! Take care of yourself! Fix yourself a dinner that you love, that maybe your partner doesn't like do much. Pamper yourself with a bath and a good book. My partner and his wife usually schedule their outside dates on the same nights, so he is out with me, while she is also on a date with her boyfriend. It works remarkably well.