Kshetra means a field and here the human body is the field. The knower of this field is Kshetrajnah.
prakrtim purusam caiva ksetram ksetra-jnam eva ca
etad veditum icchami jnanam jneyam ca kesava
idam sariram kaunteya ksetram ity abhidhiyate
etad yo vetti tam prahuh ksetra-jna iti tad-vidah (BG 13.1-2)
Arjuna said: O my dear Krsna, I wish to know about prakrti [nature], Purusa [the enjoyer], and the field and the knower of the field, and of knowledge and the end of knowledge. The Blessed Lord then said: This body, O son of Kunti, is called the field, and one who knows this body is called the knower of the field.
Kshetrajnah is the Lord who resides within the heart of every living entity and He is the one who knows about the Kshetra very well.
ksetra-jnam capi mam viddhi sarva-ksetresu bharata
ksetra-ksetrajnayor jnanam yat taj jnanam matam mama
O scion of Bharata, you should understand that I am also the knower in all bodies, and to understand this body and its owner is called knowledge. That is My opinion.
Lets chant the Holy name of the Lord and make this field/body the best abode for the Lord. Nama 16 – VishnuSahasranama