In most languages, there are distinct forms for the three persons in both singular and plural (and in the dual as well, if there is one), e.g. French moi, toi, lui/elle, nous, vous, eux/elles. But in some languages, there is person syncretism, i.e. there is a form in the paradigm of independent personal pronouns that serves for more than one person. For instance, some languages have the same form in the 1st and 2nd person plural (e.g. Haitian Creole nou), and some languages have the same form in the 2nd and 3rd person plural (e.g. Seychelles Creole zot). Note that we are not concerned with pure number syncretism here (e.g. English you for 2sg/2pl).
