What does recommended for acceptance mean?

Not always. At some universities (such as the one where I presently work, the official decision to admit a student is made at the dean's level, rather than the departmental level. In such cases, the department recommends admission; such recommendations are almost always accepted, unless something irregular has happened in the admissions process.

Another reason for careful wording like "recommended" may be that they have not yet received the expected funding that would support you, so they have to wait before they give you more definite wording.