Liaison means 'linking' two words. It is a process common to all French speakers. 

For example, when a word which ends with a normally silent consonant, as in the plural 's', the normally silent sound of 's' is pronounced as a 'z'.

In other places the normally silent 't' is pronounced as a 't',

Words that start with a vowel sound get special treatment. French likes to have a consonant 'cover' that vowel.