WHY ARE THERE GROOVE LINES ON THE "F" AND "J" KEYS ON THE KEYBOARD ??? (KEYBOARD PAR "F" OUR ''J" KEY PAR LINE KYU HOTI HAI ) ???

Hello friends welcome on my blog, aj ham janenge interesting information about keyboard, so....Friends aapne keyboard to dekha hi hoga par usse kabhi gor se nahi dekha hoga to chaliye friends keyboard ko dhyan se dekhte hai...keyboard ko dhyan se dekhne par hame "F" key and "J" key par small tactile line dikhegi so friends apke mind me ye jaroor aya hoga ke in keys par ye line kyu bani hui hai ??? so friends aj ham apko batate hai ke inn keys par ye line kyu bani hoti hai, inn lines ka relation typist se hota hai yup friends ! jab aap thik se typing seekh jate ho to apko keyboard dekhkar type karne ki zarurat nahi hoti hai our aisa hone par apko in hi lines se pata chalega ke apki konsi finger kis key par hai in hi line ka use karke typist apni finger ki position theek karte hai and finger sahi jagah par hogi tab hi thik tarah se typing hoti hai isliye inn line ka use karke typist bina dekhe typing karte hai.