when it comes to ammo lou are looking for 9mm luger for your 995 ts.
Jacketed refers to the bullet type.
There are full metal jackets or fmj. This is a lead core, with a copper jacket over the lead. All you will see it the copper part.. Use this for plinking at the range. Fmj can come in different shapes as well. the jacket prevents build up of lead in the barrel.
JHP Jacketed hollow point is defensive ammo or hunting. It has a hollow point for expansion. The goal here is little hole in that gets bigger to facilitate the bad guy or game to fall and stay down. JHP ammo also seeks to prevent over penetration.
Cast bullets, that mules mentioned, are used mostly by us reloaders. It is a way cheaper alternative to get scrap lead and cast it into a bullet. We have to do some more cleaning of the barrel to remove lead build up, but we make sure our loads are not to "hot" and this prevents most of the build up. Cast bullets are just fine, but require more cleaning.
When HP says jacketed bullets, it is more for legalese reasons than anything. If you let lead build up get excessive, it could cause the weapon to fail, causing injury to the shooter. Since most commercial ammo is jacketed, you will be fine.