For most learners of foreign languages, one of the most difficult tasks is to increase your vocabulary so that you can be more conversive in the target language. This first sentence is already more complicated than most beginning-level English students can easily digest, but it points one simple way to build up your vocabulary: finding synonyms (words with similar meanings) and antonyms (words with opposite meanings).
Take for example the word "tasks." Words that could replace it in the first sentence above include: goals, jobs, assignments, duties, chores, missions, and charges. This does not mean that all of these synonyms can substitute for "tasks" in this context. For example, the word "mission" sounds odd when used to describe a learning goal because it implies an overarching goal with specific objective and expected result. A "task" is one step in the process of learning a language and is narrow in focus. Learning synonyms helps you to make connections between related words but also improves your understanding of nuance in the target language - not all words that you see in an online dictionary query for "tasks" is going to be an appropriate choice.
Synonyms for the word "digest" in the first paragraph include break down, understand, make sense of, dissolve, assimilate, and absorb. Antonyms (opposites) include confuse, jumble, mix (up), and misunderstand. Learning words in pairs - such as opposites - quickly increases your vocabulary in a way that is easy to remember. As with synonyms, there are antonyms that can only be used in specific contexts, but there is generally one word that is used most frequently as the generally opposite meaning of the word. Here, "misunderstand" is probably the most common antonym for "digest" in the sense of "to understand."
This method works best with adjectives, verbs, and adverbs, as many nouns do not have specific opposites (e.g. airplane, car, flower, dog, etc.), even if they have synonyms. Interestingly, there is quite a bit of research in linguistics (frame semantics) to back up the idea of learning vocabulary specific to a concept.
The theory of frame semantics suggests that relational knowledge surrounding the concept (e.g. "farming") is critical to understanding and being able to speak about a particular topic (this is used extensively in AI and computational linguistics research). It is not meant as a means to learn every related word to "farming," for example, but rather, it presupposes a certain amount of knowledge required to be able to converse about a topic and continue to explore it in depth. By learning more paired words (synonyms, antonyms, etc.) and understanding their uses in context, you expand not only your vocabulary but also your knowledge of how they work together to create meaning.