In simple words
In Vedic astrology your life moves through nine long chapters called dashas, always in the same order. Which one you start in depends on your Moon at birth.
The Mars dasha lasts 7 years. While you are in it, Mars's themes colour those years. Your chart page in Vedic mode shows which dasha you are in now, with dates.
Themes
The Mars period lasts seven years and brings energy, ambition and initiative. It is often a time of competition, property matters, physical activity and bold decisions. Energy is high, and so is the potential for friction, so physical outlets and clear goals help a great deal.
What it supports
Courage, sport, technical skill, property and land, defending what matters and starting ambitious projects.
What it asks of you
Mars asks you to direct your energy wisely. Use strength to build and protect, and manage anger before it manages you.