Dentures are sets of false teeth mounted on plastic that are worn in the mouth to replicate the functions of teeth. You might need dentures if you have lost all of your teeth or a partial denture if you have just lost some of your teeth. They can be held in place via your gums' natural suction ability or using a fixing agent.
In the past dentures tended to be made en masse and were all the same, now you are far more likely to have hand crafted dentures made for you by your dentist to fit the unique shape of your mouth. This is not the only thing that has changed about dentures. They are also far more comfortable than they used to be. Patients in the past used to frequently complain about friction on their gums caused by their dentures rubbing. Friction-free dentures are now available which are far easier for the wearer but, given that they are so sensitive, gums still need to undergo a certain degree of hardening as they get used to dentures.
The fact that dentures are hand-made now for individual patients means that they are far more realistic and wearers are less likely to be self-conscious about the way they look. What still concerns many denture wearers though is the possibility of them slipping out during speech, eating or drinking. Unfortunately this is something that is unlikely to ever be fully ruled out. The fact is that dentures are removable and as such it is possible that they will slip out. That they are tailor made means this is less likely than it used to be because they are fabricated especially to fit the wearer's gums snugly.
Dentures can become messy too and there is nothing worse for the wearer than getting food trapped between the denture and the gum. Again, this is part and parcel of the fact that dentures are removable and some even find it convenient that they can take their dentures out to clean them.
Dentures can be seen as a short term solution for tooth loss while you are making up your mind about whether to opt for a more permanent one like dental implants. Dental implants, for example, are expensive and require invasive treatment whereas dentures are relatively cheap and don't require surgery.
You should talk to your dentist about the options available to you if you have suffered from tooth loss.