What is Alankar?
In Hindustani Classical Music, Alankar or Alankara means ornaments or adornments. Alankara is also referred to as Palta at times. Alankar is integral to the core essence of Hindustani classical music. The earliest reference to the term Alankar can be been found in Bharata’s Natyashastra, which was written sometime between 200 BC and 200 AD. This treatise talks about the 33 types of Alankars. Other musical treatises like Sharangdev’s Sangeet Ratnakar in the thirteenth century and Ahobal’s Sangeet Parijat in the seventeenth century states that there are 63 and 68 types of Alankars respectively .
The Shastras or ancient texts have categorized alankars into two broad groups – Varnalankar and Shabdalankar. The set of alankars that constitute the Varnalankar group is sthayi, arohi, avarohi, and sanchari. Sthayi refers to halting at a single note, arohi to an upward movement, avarohi to a downward movement and sanchari is a mixed (upward and downward) movement. This classification of alankars related to the structural aspect of a raga. Now the other group of Alankars is called Shabdalankar. It comprises the aesthetic aspect. It makes use of the sound production technique utilised by either the human voice or of an instrument. All the variations that a performer creates during a performance within a raga and tala limits could be termed as alankar, because all these variations constitute in enhancing the beauty of the raga, the tala and the composition .
What are the types of Alankar?
The alankars in common use today are Meend (varieties of glides linking two or more notes), Kan (grace note), Sparsh and Krintan (both dealing with grace notes – especially as applied in plucked stringed instruments), Andolan (a slow oscillation between adjacent notes and shrutis), Gamak (heavy forceful oscillations between adjacent and distant notes), Kampit (an oscillation or a vibrato on a single note), Gitkari or Khatka (cluster of notes embellishing a single note), Zamzama (addition of notes, with sharp gamaks) and Murki (a swift and subtle taan-like movement) .
How does practicing them help you?
Well, alankars and palte are vital for you to gain voice control and sing with grace! It also helps you to sing proper notes when you have to skip notes according to a raga’s structure . In the video below, listen to how Javed Ali glides through the swaras. His capability comes from the rigorous practice of alankars/palte. Listen to his tips on how to do Riyaz.
References used for this article  - http://www.itcsra.org/Study-of-Alankars  - http://learnraagabasics.blogspot.com/2013/08/basic-training-alankaar-paltaa.html