Nanonood means "watching" (progressive active verb).
Pinapanood means "being watched" (progressive passive verb).
Nanonood ang mga tao ng basketball.
The people are watching basketball.
Ang basketball ay pinapanood ng mga tao.
"The basketball is being watched by the people".
However, when we use pronouns as the doer of the verb, we can construct a Filipino sentence in 2 ways:
Karaniwang Pangungusap (Regular) and Di-Karaniwang Pangungusap (Irregular).
The "Karaniwang" format is easily identifiable by the presence of "ay" which is the "be verb (is/am/are)" in English.
Consider this example:
[active voice, intransitive verb (no direct object)]
Ako ay nanonood. (I am watching.) (Karaniwan)
Nanonood ako. (I am watching.) (Di Karaniwan)
[active voice, transitive verb (with direct object)]
Ako ay nanonood ng basketball. (I am watching basketball.) (Karaniwan)
Nanonood ako ng basketball. (I am watching basketball.) (Di Karaniwan)
[passive voice, transitive verb (with direct object)]
the passive voice should always use transitive verb
Ang Basketball ay pinapanood ko. (Karaniwan)
Pinapanood ko ang basketball. (Di Karaniwan)
(Literally means "Basketball is being watched by me", but that is awkward, so it is loosely translated as "Basketball is what I watch" or "I am watching basketball.", but that would lose its original voice that the verb intended.)
Filipino verbs are conjugated (binabanghay) more extensively than the English verbs. This grammar rule might be confusing to you if you are new to this, but this is the only way that you could systematically understand how a Filipino sentence is constructed. Familiarize yourself with the grammar rules. :-)