Person:

First (1st) - subject is the person speaking
Second (2nd) - subject is the person being spoken to
Third (3rd) - subject is the person or thing being spoken about

Number:

Singular (sg.) - subject is just one person or thing
Dual (dual) - subject is a pair of persons or things
Plural (pl.) - subject is more than one person or thing

Voice:

Active (act.) - the verb's subject performs the action
Passive (pass.) - subject is acted upon by someone or something else
Middle (mid.) - subject performs an action for itself or on something of special interest to it

Mood:

Indicative (indic.) - statements of fact, reality, or actual occurrences
Imperative (imper.) - commands
Subjunctive (subj.) - contemplated or imagined actions
Optative (opt.) - further removed than subjunctive

Tense:

Present (pres.) - present time, imperfective or aoristic aspect
Imperfect (imperf.) - past time, imperfective aspect
Future (fut.) - future time, imperfective or aoristic aspect
Aorist (aor.) - past time, aoristic aspect
Perfect (perf.) - present time, perfective aspect
Pluperfect (pluperf.) - past time, perfective aspect
Future Perfect (fut. perf.) - future time, perfective aspect