na-adjective
Used as a na-adjective to describe something that is concentrated, thorough, or high-intensity, similar to English 'intensive'.
このコースはインテンシブな内容で、短期間で多くのことを学べる。
This course has intensive content, allowing you to learn a lot in a short period.
集中的 is a native Japanese na-adjective meaning 'concentrated' or 'focused', often used for efforts or activities. インテンシブ is a direct loanword and carries a nuance of high intensity or thoroughness, often in educational or training contexts.
Borrowed from English 'intensive'.