It’s a word used it is generally a derogatory term used to describe Hetrodox Catholics who disagree with one or more points of Catholic Doctrine or Dogma, a pick n’ mix approach if you will. These could be any points, but points of disagreement are usually women priests, infallibility, divorce, the position of protestant churches, homosexuality and contraception.
Seeing as there are several elite theologians and priests such as Hans Kung who reject doctrines like Papal Infallibility yet have not been formally excommunicated (and in the case of Benedict held regular meetings with them) it is fair to say that he, and those like myself who agree with his opinions can still nominally at least be considered Catholics.
I think I am fairly typical Cafeteria Catholic. I have no qualms with the vast majority of church teachings such as the real presence, the leadership of the Pope. the importance of the sacraments or the role of Mary but I reject infallibility and the teachings regarding contraception and homosexuality. Upon divorce I’m more ambivalent, but am increasingly finding more merit in the Orthodox theology on the topic. I really am not well versed enough upon debates raging over female ordination to hold an opinion either way.
If anything I’m more on the conservative end of the scale if there is one. But this is a fairly typical example.
I have not received the Eucharist for about two years(?) because I am led to understand that to take communion I must attend regular confession (I do not consider rejection of infallibility and such to be a sin but I do sometimes do other things that are) but because of those doctrinal disagreements I am not eligible for absolution (I could lie to obtain it, but that would be rather pointless). That said, I would say the vast majority of them still do, because they believe they are in the right and the current teaching is incorrect (hence why would they abstain).
I would hazard a guess that around 80% of Catholics in France are of this variety, even higher in the UK (in all my meetings with Catholics and tours of schools there I have only met one who could be considered an “Orthodox” Catholic, and he was a Bishop). The largest concentration of them seem to be in Germany.