"Tell the believing men that they should restrain their gaze, and guard their private parts and chastity. This is what is purer for them. God is fully aware of all that they do". (24:30)
In this verse Allah SWT is telling the believing men that they should protect their eyes and keeping their gaze lower and not stare at the women. and in next part of the verse Allah SWT is also telling believing men about protecting their private parts. So I hope you understood now what is Men's Hijab?
Its very common now a days that men specially young boys stares at women on the roads, in markets and all open places. those people who do it are clearly going against the Orders of Allah SWT and his Prophet SAW.
suppose you are going on a road and suddenly you see a women then you should quickly lower your eyes. there is a Hadith of Rasool Allah SAW according to which there is no sin for first accidental gaze but you should Immediately lower your eyes after first gaze. according to another hadith starring at women is zina of eyes.
Remember gazing at women is first step to wrong path and next step which Haram gazing will cause is Zina so be really careful.
I am also a young man of 24 years and I can understand how difficult It is to protect your gaze in today's time. but Remember by protecting your eyes you will be earning a great reward which will benefit you in the hereafter as well as in this world Inshallah.