In addition to Mr. Dane's comments, a lawyer would also file a 995 motion if additional charges were added after the preliminary hearing if the "new" charges are not "transactionally related" (conduct which occurred during the commission of the charged offense). This assumes that there was an objection at the time the evidence was offered.
Also, you can file a 995 motion based on a denial of a substantial right - e.g., you did not have an attorney, your attorney was not was allowed to conduct an adequate cross-examination, etc..
I assume you mean a 995 motion. That's a motion to set aside the information (the charging document filed after a preliminary hearing). The basis is that the prosecution failed to present sufficient evidence to hold the defendant for trial and the court held the defendant on one or all charges without sufficient probable cause.