Aaradhak means the one who practices and honors the path of tapas (austerities) with faith and discipline. In Jainism, there is a framework called the 20 Sthanak Tap, which guides a seeker on twenty important austerities or penances. An “aaradhak of 20 sthanik tap” is someone who follows these twenty practices as part of their spiritual purification.

Key points:

• The 20 Sthanak Tap are composed of two broad groups: external (bahya) tapas and internal (abhyantara) tapas.
• External tapas (6) involve bodily practices and restraint:

- Anashana: fasting for a set period - Unodari (Avamodarya): eating less than one’s hunger - Vritti-sankshepa: limiting types/amounts/times of food - Rasa-parityaga: giving up tasty or stimulating foods - Kaya-kleśa: bearing bodily hardship with patience (tolerance of heat/cold, etc.) - Sanlinata (sometimes Vivikta-śayyāsana): seclusion and restraint of movement and senses

• Internal tapas (6) involve mental discipline:

- Prayaścitta: repentance/atonement - Vinaya: humility and reverence - Vaiyāvṛttya: selfless service to ascetics and to those in need - Svādhyāya: study and reflection on scriptures - Vyutsarga/Kāyotsarga: letting go of attachment to the body - Dhyāna: proper meditation

• The remaining twelve items (to reach twenty) are additional practices often including samayik (meditation in time), chhedopasthāpana (confessional atonement), upavasa (fasting on holy days), ayambil (plain-food fasting), and other related vows or practices; traditions vary slightly in naming and order between Śvetāmbara and Digambara.

Note on tradition:

• Both Śvetāmbara and Digambara traditions accept the core twelve (six external + six internal). The exact list and labels for the extra items can differ by tradition, but the aim is the same: purify the soul, reduce karmic influx, and progress toward liberation.

You can read more here

If you’d like, I can summarize one or two specific 20th-tapas in more detail (for example, how ayambil or samayik is practiced according to a particular tradition).