Shaktism is a Hindu spiritual tradition focusing worship upon Devi, the Goddess, the Divine Mother who creates and embodies all the Universe.

While Hindus in general conceive of Devi as the Shakti (Supreme Energy) of Shiva (Supreme Consciousness), Shaktas worship Her as Brahman (the Ultimate Godhead), holding that all other forms of Divinity are but Her diverse manifestations.

Achieve worldly contentment, divine enlightenment and ultimate liberation: Surrender to Shakti, the Divine Feminine!

I think in olden time,worshippers stood either by Shaiv,Vaishnav or Shakta Sampradaya [streams].
I think, Shakta were those worshipping GOD inshape of female deity,say Durga,Kaali,Bhadrakaali,& Dasa Mahavidyas ,may be through Tantra too.