Kerning is a term used in typography and refers to the spacing between letters. It is different from tracking in that tracking adjusts the space between letters evenly while kerning adjusts the space based on character pairs. In a well-kerned font the space between characters is the same or has similar area.
Sometimes when we make text really big or use certain fonts the kerning will be off and there will be too much (or too little) space between certain characters. Typical character pairs are V & A or W & A but it can be off on others as well.
When bad kerning happens in our text we must adjust it to bring back good balance in the text and increase legibility. Below is an example with a Before and After showing the original text with no adjustment and then the text with adjustments. In this example the kerning issues are on the number 100,000, particularly noticeable between the 1 and the first 0. The space appears much bigger than between the rest of the characters. I also adjusted a bit between the second 0 and the comma. The after shows a much more balanced 100,000. So remember to check your kerning and adjust if necessary.
Image Credit: mokra