Comprehensible Input

 An essential activity for learning a language is getting lots of input. Immersing yourself in the target language makes you familiar with the sounds of it and how to naturally say things. It also exposes you to real-life usages of the vocabulary and grammar you learn. Those effects interact with what you already know about the language to reinforce and connect information.

The most effective kind of input for learning a language, however, is comprehensible input. Dr. Stephen Krashen, a professor of education at the University of Southern California and a leading researcher in this field, has said that optimal input has four aspects:

1. Comprehensible: You should understand most of it, even though there can be some unknown vocabulary and grammar.
2. Compelling: The content should interest you so much that you do not mind that it is in another language.
3. Quality: The content should be rich and language, and the language should make the message of the content understandable. It should also introduce vocabulary and grammar that is one step above what you already know.
4. Quantity: Although input will get you to competency (In another article, Krashen goes so far as to say that input is the only thing you need), you need a lot of input to get there.

(Source: "Optimal Input" by Stephen Krashen)

That being said, here are some resources for input:

• Refold : Online crash course on their immersion method + resources for various languages
  
• Comprehensible Input Wiki : Library of resources for 80+ languages
  
• Comprehensible Japanese : Youtube channel
  
• Tadoku.org : Leveled books in Japanese; very beginner friendly