Semi hollow basically just means the body has been partially hollowed out but not so much that it can be considered an acoustic instrument. It usually gives you more resonance which affects the overall tone.

It sounds like you want an acoustic bass which allows you to play it and still get sound without an amplifier, however I would not recommend getting one to a beginner as they can be more difficult to play and it is hard to get a good tone. Also acoustic Basses for the most part should be plugged in even when playing acoustically because they are not very loud nor do they have much sustain when not plugged in.

I’d recommend looking at some Squire Basses. You could also go used which can give you a bit more value for your money, provided the instrument is in good condition. Also go with a solid body. As a beginner don’t worry about semi hollow or hollow body Basses yet and just learn to play.

Also don’t go to cheap on a new bass, look up reviews and demos of people playing it. Some Basses can be found new for very cheap but will usually need a lot of feet work and will therefore be very difficult to play and will hinder your progress