API stands for Application Programming Interface and is simply the underlying code structure that lets different applications speak to each other.
curl -XGET 'https://podcastplus.net/api/podcasts/search?q=KEYWORD' -H 'X-Api-Key: YOUR_API_KEY'
or
curl -XGET 'https://podcastpl.us/api/podcasts/search?q=KEYWORD' -H 'X-Api-Key: YOUR_API_KEY'