0405:

BEM - block element modifier

<div class="hand">
  <div class="hand__finger hand__finger--thumb"></div>
  <div class="hand__finger"></div>
  <div class="hand__finger"></div>
  <div class="hand__finger"></div>
  <div class="hand__finger hand__finger--pinky"></div>
</div>

Block - nadrzędny element Element - częśc bloku Modifier - modyfikator