The Sidh Gohst (Dialogue With The Sages) is a pious Bani that recounts a meeting of Guru Nanak with a group of Hindu ascetics (siddhs) who had renounced the world, living in the caves of the Himalayas. They believed that mental and physical exercises were necessary for acquiring magical powers (also known as siddhis) that would lead to the attainment of liberation. 

While such ascetics believed one must withdraw from society and ones family, Guru Nanak's believed that liberation can be attained while living in the world as a truth-oriented 'householder' who earned his living by honest work. For Guru Nanak, true yoga is a meditative remembrance of the Word combined with Seva (selfless service) to those in need in the community.

Guru Arjun Dev collected Guru Nanak's accounts of these meetings and included it (in musical measure) in the Guru Granth Sahib (pages 938-946). The Sidh Gosht recounts Guru Nanak's discourse between Guru Nanak and the Nath yogis Bhangarnath, Chaqrpatnath and Luhairipaa.

The Sidhs Questions

ਕਵਨ ਤੁਮੇ ਕਿਆ ਨਾਉ ਤੁਮਾਰਾ ਕਉਨੁ ਮਾਰਗੁ ਕਉਨੁ ਸੁਆਓ ॥

kavan tumē kiā nāu tumārā kaun mārag kaun suāō .

(Sidhs)"Who are you? What is your name? What is your way? What is your goal?"

ਸਾਚੁ ਕਹਉ ਅਰਦਾਸਿ ਹਮਾਰੀ ਹਉ ਸੰਤ ਜਨਾ ਬਲਿ ਜਾਓ ॥

sāch kahau aradās hamārī hau sant janā bal jāō .

(Guru Nanak Dev Ji)"I speak the truth. This is my humble request, I am simply a sacrifice to the serving Sants."

ਕਹ ਬੈਸਹੁ ਕਹ ਰਹੀਐ ਬਾਲੇ ਕਹ ਆਵਹੁ ਕਹ ਜਾਹੋ ॥

kah baisah kah rahīai bālē kah āvah kah jāhō .

(Sidhs)"Where is your seat? Where do you live, O child? Where did you come from, where are you going?"

ਨਾਨਕੁ ਬੋਲੈ ਸੁਣਿ ਬੈਰਾਗੀ ਕਿਆ ਤੁਮਾਰਾ ਰਾਹੋ ॥੨॥

nānak bōlai sun bairāgī kiā tumārā rāhō .2.

(Guru Nanak Dev Ji)Nanak speaks, (The Sidhs have said) "O detached one, listen. What is your path?"||2||

Guru Nanak Dev Ji's answers.

ਘਟਿ ਘਟਿ ਬੈਸਿ ਨਿਰੰਤਰਿ ਰਹੀਐ ਚਾਲਹਿ ਸਤਿਗੁਰ ਭਾਏ ॥

ghat ghat bais nirantar rahīai chālah satigur bhāē .

(Guru Nanak Dev Ji)"(The One pervades in) each and every heart, that is where I sit, that is where I focus and dwell (this is where I am at peace). I walk in the will of the True (eternal) Guru (this is my way)."

ਸਹਜੇ ਆਏ ਹੁਕਮਿ ਸਿਧਾਏ ਨਾਨਕ ਸਦਾ ਰਜਾਏ ॥

sahajē āē hukam sidhāē nānak sadā rajāē .

(Guru Nanak Dev Ji)"Naturally (in the Hukam) I came (into this world). In Waheguru's Hukam, I go. I am Nanak, forever walking according to Waheguru's Hukam."

ਆਸਣਿ ਬੈਸਣਿ ਥਿਰੁ ਨਾਰਾਇਣੁ ਐਸੀ ਗੁਰਮਤਿ ਪਾਏ ॥

āsan baisan thir nārāin aisī guramat pāē .

(Guru Nanak Dev Ji)"The eternal, imperishable Waheguru, (in reality) is the one who sits and dwells, this is the teaching of the Guru I have obtained (this is my goal)."

ਗੁਰਮੁਖਿ ਬੂਝੈ ਆਪੁ ਪਛਾਣੈ ਸਚੇ ਸਚਿ ਸਮਾਏ ॥੩॥

guramukh būjhai āp pashānai sachē sach samāē .3.

(Guru Nanak Dev Ji)"The Gurmukh understands, they come to recognise themselves, they merge in the Truest of the True." ||3||

Imperfect translation, it was actually pretty hard to translate some lines. There are a few ways to translate and interpret them. I also lack the spiritual state, so I guess my understanding won't do this justice.

Guru Nanak had such discourses with various Yogis during his Udasis, at such places as Achal Batala, Nanakmata and Nanded.