Traditionally, av systems have what is termed 5.1 capability. All that means is you have 5 sources of sound, one from the centre of your TV, one from the right front, one from the left front and two speakers behind you, left and right. That gives you realistic Surround sound. A subwoofer is added to deal with low frequency bass sounds like for example explosions. A soundbar simply takes the front three speakers and encloses them in a single cabinet. Sorry to be long winded but to answer your question specifically, yes it will make a big difference, but where it will make a massive difference is where you combine it with rear speakers and a subwoofer. That will make a difference that you will not believe when compared with sound from your tv. Do it right and it will be comparable to having your own cinema. The simplest way of doing this is wirelessly through a system like sonos where you don't have to worry about amplifiers, cabling etc. You will need sonos soundbar, rear speakers and subwoofer. The kit isn't cheap but it is very high quality and an absolute doodle to set up and use. You would also be able to stream music through the system so it would look after your av and music needs. Sonos service is also the best in the business. I use it throughout the house for my music and my son uses it for his AV system. I can absolutely recommend it. A sonos sound system along the lines I described will cost you best part £2k but will be worth every penny. And no I don't work for sonos! PM me if you want more detailed info.
