Gerunds are verbs, that are not used as verbs and instead have been turned into nouns and they always end in -ing. Gerund Examples: "Swimming is fun." "Drinking a lot of wine gets you drunk." "Running is hard" So you can compare, here is an example of a verb ending in -ing that is not a gerund: "He is running towards the finish line." "I am baking cookies." Infinitives are similar to gerunds because they are also verbs, that are not used as verbs, but instead have been used as either a subject, object, or even complement. Infinitives are left in their plain form w/ no prefix or suffix modifying it and are almost always preceded by the word "to". Infinitive Examples: "I love to sing." "Jose likes to swim." "It is important to drive safely." "To ace the exam he needs to study hard." "He wants to call the pretty girl, but he is too shy." Here are example sentences, where "to" is a preposition and there is no infinitive so you can compare: "I went to the store." "Delia brought her dog to the park."

Olivia has explained what gerunds and infinitives are, but I'm guessing that your question really is 'What's the difference?' 'When do I use them?' 'Why is there a gerund in that sentence but an infinitive in this one?' The best advice I can give is not to try and translate them. If you start to compare each sentence to the equivalent in Spanish, you will get nowhere. Start by looking at a grammar book or grammar webpage (just google your question if you don't have a grammar book), and look at some lists of common English phrases using gerunds and infinitives. Try to learn some of them, and do your best to use them. Listen, read, and notice when native speakers use them. After a while, the correct forms will sound right to you.