Could anyone tell me what the meaning of "-t-" in these sentences is? Avec l'article definir, que se passe-t-il? Conbiem de fois y utilise-t-on la conjonction ni?
There is absolutely no meaning to -t-. It's there to make it easier to say and to avoid two vowels from colliding: passe-il (e-i) and utilise-on (e-o). The french don't like their vowels colliding.
For someone who's learning french, there are a lot harder words to say than passe-il and utilise-on but we don't have a say in how their language should be :-(
It means nothing. It's added when an inversion occurs and the second word begins with a vowel that can't be linked with a 'liaison' with the first word, so an artificial one is created by including that 't'.
A liaison is when a word ends with a consonant and the next one starts with a vowel and both sounds are linked phonologically. For example, when you pronounce 'ils ont' like ' il zon', linking the last 's' with the initial 'o' of the conjugated verb.