What does OVA stand for?

"OVA" or "Original Video Animation" is basically a direct to video release. Production values are usually high meaning that animation is usually superb. The acronym OAV (Original Animation Video) may be used in place of OVA.

TV series, in general, have lower budgets and expectedly, the quality of the animation and score suffer. As always, there are exceptions to the rule. High quality series such as The Vision of Escaflowne (Tenkuu no Escaflowne) and Neon Genesis Evangelion (Shin Seiki Evangelion) often meet if not surpass OVAs in terms of quality.

Theatrical productions . As with anything released in the theater, the overall strength of the animation is not guaranteed. But animation of the highest order and at the very least, an orchestral score, are the norm.