The infinitive is the base form of the verb, before the verb is conjugated. For example: to speak, to eat, to live are English verbs in the infinitive form; to + verb creates the infinitive of a verb in English. In Spanish the infinitives of verbs have three diferent endings: ar, er and ir.
Light dependent reactions produce ATP and NADPH from energy captured from light. Therefore without light it cannot proceed. Light independent reactions fix carbon dioxide into glucose using the ATP and NADPH produced in the light dependent reactions. So light independent reactions can occur without light as long as CO2, ATP and NADPH is present.
These energy carriers drive the light-independent reaction, which uses the carbon dioxide and ATP from the earlier step to actually makes the glucose. For most plants on a typically sunny day, when the sun goes down the light-dependent reaction stops, but the backlog of energy carriers it has made may keep the light-independent reaction going until the middle of the night.