title: What does conda do when "solving environment"
body: <p>Whenever I run <code>conda install/remove/update &lt;package&gt;</code>, it tells me it's "Solving environment" for some time before telling me the list of things it's going to download/install/update. Presumably it's looking for dependencies for <code>&lt;package&gt;</code>, but why does it sometimes <em>remove</em> packages after doing this operation? For example, as I was trying to install Mayavi, it decided it needed to remove Anaconda Navigator. </p>
  
  <p>Furthermore it does not provide an option to perform only a subset of the suggested operations. Is there a way to specify that I don't want a package removed?</p>