Is there a difference between tazkiyah and ihsaan? In short, YES.
Tazkiyyah is a Quranic term
Ihsaan is a hadeeth term
– Takhliya – remove diseases of heart
– Tahliya – beautify the heart with good traits
2 stations of ihsaan:
– worship as though you are witnessing Allah – first or higher station – mushaahada
– worship as though Allah is witnessing you – second or lower station – muraaqaba
Science of Tasawwuf originated from the concept of tazkiyah and ihsaan. Just like the sciences of fiqh, hadeeth, tafseer, creed and Arabic grammar, etc., tasawwuf is also a science that deals with tazkiyyah and ihsaan.
The ‘path’ to achieve tazkiyyah or ihsaan or tasawwuf is tareeqah or sulook. Other relevant terms are maslak and madhhab .