Nominalization is a process of clauses taking on some noun properties, in particular becoming eligible to serve as arguments and modifiers to verbs.
For example, in Modern Standard Turkish (MST), like in many Turkic languages, the verb can be nominalized with a special affix, take some person and number inflectional affixes (but not the TAM markers; and the finite verb's inflectional paradigm and the nominalized verb's inflectional paradigm are generally different in MST), then take noun case markers after that. The verb's subject takes genitive case:
Ali-nin gecen aksam nehr-in kenar-in-da kos-tug-un-u gor-dum
Ali-GEN past evening river-GEN shore-3.SG-LOC run-FN-3.SG-ACC see-PAST.1.SG
I saw that Ali was running along the river the other evening (Kornfilt).
There are different kinds of nominalization. In particular, some nominalized verbs can be modified by adverbs (like regular verbs):
Kim instantly eating the pizza did not surprise anyone.
while others can be modified by adjectives, like nouns:
Kim's instant eating of the pizza did not surprise anyone.
In some languages (e.g. Japanese), the nominalized verb that can be modified by adverbs needs to keep the case frame of an indicative clause, however that is not the case in e.g. Turkic languages, where the nominalized verbs with genitive subjects can be modified by adverbs (Asarina and Hartman). In this questionnaire, you have an option to implement "high" or "low" nominalization; that means the verb will be nominalized "higher" or "lower" in the tree. In the case of "high" nominalization, there will be a verby constituent which will then be turned into something nouny; in contrast, with "low" nominalization, the verb is turned into something nouny and then a nouny constituent is formed with its arguments.