Sloka : A pair of successive lines of verse, typically rhyming and of the same length. Most Hindu scriptures are written in forms of slokas. Mahabharata, Ramayana & Upanishads are written in the form of slokas. The first sloka of Mahabharata is “Narayanam namaskrutya naram chaiva narottamam Daivim sarasvatim chaiv tato jayamudiryet”
Stotra or Stotram is a sanskrit word that means a ‘hymn of praise’. Stotras are the hymns written to praise the Gods. One famous stotra is Shiva Thandava Stotra.
Stuti literally means praise or glorification. Stuti is a general term for devotional literary compositions. Stutis are prayers offered to Gods. Stuti can be done by reciting bhajans, mantras , stotras and other forms.
Mantra is a sacred utterance, a syllable or group of words believed to have religious , magical, psychological and spiritual powers. Most famous mantra is Gayatri Mantra which as follows: Aum
Bhur Bhuvah Svah
Tat Savitur Varenyam
Bhargo Devasya Dheemahi
Dhiyo Yo nah Prachodayat