Last night I was randomly surfing astronomy pages and came across this.I searched up Wikipedia and other sites,but it doesn't exactly give me enough information about their characteristics.
I'll try to add a bit of context to the Wikipedia article, though the major references are all available there. The article covers things like the potential formation mechanisms but I guess doesn't really put them into scientific perspective.
Consider, for a moment, a red giant of one solar mass, far up the red giant branch. It has a deep convective envelope, at the bottom of which there is a shell of hydrogen fusing into helium, all surrounding an inert, highly degenerate helium core. The core at this point is much like an isolated white dwarf. So, back in the late 1970's, Kip Thorne and Anna Żytkow tried to model (Thorne & Żytkow 1977) what would happen if you replaced the white dwarf with a neutron star. Such hypothetical objects thus became known as Thorne-Żytkow objects (TZOs).
TZOs have mostly remained theoretical exotica, at least in part because it's very difficult to distinguish them from "ordinary" red supergiants. The main giveaway would be the presence of unusual elements in the atmosphere, produced by the much hotter nuclear reactions happening in the fusion shell around the neutron star core. There have been just a handful of papers published about them, almost all by theoretical groups, in the intervening 40 years.
PS, following comment: The consensus view is that a single star couldn't form a TZO because if the core collapses into a neutron star, models predict that the envelope will be ejected. That is, single star's only evolve into "naked" neutron stars. Under this assumption, the only way to form a TZO is to have a neutron star collide with or accrete enough material from another star. This could happen if two wandering stars collide. Alternatively, it could happen if one star in a binary collapses into a neutron star. In particular, it's known that the collapse process is probably not symmetric, so the neutron star gets a "kick" in some direction. If the neutron star is kicked into the companion, it will presumably undergo some viscous drag and settle into the centre.