Search actions act like a search engine - pass in the keywords (some actions ask for the exact keywords, some actions ask for partial keywords) and the details of the matching object will be provided to you. If Search actions don't find a matching object, the action will not fail, neither will they return anything. This might cause subsequent actions expecting values to be passed to them to fail. You can also think of Search actions like a filter that filters the specified conditions, and all the subsequent actions will be based on the specified "filter". Do note that when running a search, you should only use ONE unique field for searching. If you fill in two fields, search results will only show matches that fulfill both fields together, not one or the other.
Get actions are more pinpointed - they require a unique ID to be passed to them, and the details of the matching object will be provided to you. If Get actions don't find a matching object, it will fail immediately. IDs used for get object are often mapped from previous steps.