A keyword is exactly what it sounds like. It’s a keyword that writers incorporate in order to rank with a search engine. When users search for that keyword, only pages containing that keyword will be returned.
Long-tail keywords are multiple keywords or specific phrases.
The idea behind long tail keywords is that there is a market for every product or service, but that market might be small.
Long-tail keywords might get less frequent traffic, but produce a higher conversion rate because the person searching with this level of specificity is more likely to be further along the purchase journey.