What does introductory period mean?
The introductory period is usually a period of a few months (sometimes 6, rarely even more) in which the new card holder will pay a lower APR than the standard he has to for the rest of the term. That is why it is advisable tat you firstly have a look at the standard APR you have to pay for a number of years when taking a loan, and not at the introductory rate which is only in force for a short period.
It is very rare however it may happen that you can afford to pay back the owed balance within this 0/very low APR period. So, if you have a loan of $2,000 for one year (fixed rate), with an introductory 6 months APR 0, that means if you can manage to pay back around $333/month for a period of six months, you manage to pay back the amount in full without any interest. That is why you always check the standard APR, and decide from beforehand whether you intend to have this card for a long period or is it only a short term solution for you.