The learner doesn't know

People learning English as a second language often have trouble knowing when and when not to use articles. Often, this is because the learner does not know whether the noun was countable (and whether the countable known is plural or singular) or uncountable. It is important to know count versus non-count nouns.

https://cegepenglish.zendesk.com/hc/en-us/articles/202713955-Generalizations-Non-Specific-References-When-to-Use-a-the-or-plural-s-?mobile_site=true

Why have they used "the" before "learner"?

I thought it is used in general sense not any specific learners.