What is the essence of BEM?

Question

BEM

Is the essence of BAM to avoid cascading? Is it always necessary to give classes if you are typing according to BAM . I
just started to typeset according to this methodology, more precisely, I am just learning ..
And is the markup done correctly

<header class="header">
    <div class="container">
      <div class="header-logo">
        <img class="header-logo__img" src="images/logo.svg" alt="logo">
      </div>
      <nav class="menu">
        <ul class="menu-list">
          <li class="menu-list__item">
            <a class="menu-list__link">Features</a>
          </li>
          <li class="menu-list__item">
            <a class="menu-list__link">Works</a>
          </li>
          <li class="menu-list__item">
            <a class="menu-list__link">Our Team</a>
          </li>
          <li class="menu-list__item">
            <a class="menu-list__link">Testimonials</a>
          </li>
          <li class="menu-list__item">
            <a class="menu-list__link">Downloand</a>
          </li>
        </ul>
      </nav>
    </div>
  </header>

Answer 1

https://en.bem.info/methodology/solved-problems/