The problem is probably that you named your image ‘image’. That’s the name of a quite useful core MATLAB function you will likely want to use. (This is called ‘overshadowing’ — in this instance overshadowing the funciton name with your variable name.)
This works:
I = imread('charuleelaa vanilavarasu_1.jpeg');
gray=rgb2gray(I);
figure(1)
imshow(gray)
