If a student doesn't know a thing about basketball, it is going to be exceptionally difficult to comprehend a reading passage about a basketball game.  A student who comes from a different country may have had vastly different experiences than we have had.  We must build their background knowledge before we dive into a lesson or read a passage.  

Some ways to build background: 
Visuals
Videos
Go on a field trip
Virtual Field Trips

We must also activate prior knowledge before we dive into a lesson.  Make a connection to prior lessons or connect a lesson to the students' lives.  One way to do this is to use an anticipation guide.   Before students read a passage, or before you teach a minilesson, the students respond to statements about the subject matter.  An agree or disagree activity or a true or false activity.

Another way to activate prior knowledge is to use a KWL chart.  What do we know about this topic already? What do we want to know?  After the lesson, what did we learn?

You could even ask the students to respond to a few questions that start with "What would you do...?"   

Before an ELA minilesson, have the students respond to a do now question in which the students must make a prediction about what the character will do next, and ask them why they think the character will do that.  Have them base their answer on what the character has done previously.

Here is a video from teachingchannel.org about activating prior knowledge.  It also demonstrates a great activity for teaching active listening.

​You can read more about background knowledge here.

​You can read more about front loading vocabulary here.