This quote is about fighting unjust laws through group non-compliance. Here is how it works: let's say someone (who shall go unnamed) has made it illegal or otherwise unfeasible for farmers to save their seeds. According to the law or insane circumstance, they must now buy another batch of seeds in order to plant another harvest instead of being able to use seeds to spread crop. To fight this law, a few individuals stand up and practice non-compliance. What Gandhi says in this quote is that the moment they stop ignoring you and meet this non-compliance with violence or oppression, you will win.
It may not happen right away. The very first person to stand up to this most unnatural law might be silently shut down or otherwise legally bullied into submission. However, she may also have caused one more person to question whether or not this law was just. The cycle continues. More people start thinking and find the law unjust. Soon all the farmers of a town rally together and all save their seed. How do the local enforcers respond? Do they arrest all of them and instantly take away a town's food production? They know it will cause a stir and they know it will affect them as well, yet the order comes from on high-- they cannot let this show of defiance go unchecked. The lawmakers stand up and show their true colors. And now everyone can see it. The law becomes seen as unjust because the true reason for the law has come to light. It is now known that the law has a greater import than the protection of the people. Change soon follows as it has throughout all our histories.
This is what Gandhi was talking about. First they ignore you [or silence you so others remain ignorant], then they fight you, and then you win. It is not about overcoming their laws. It is about lifting the veil pulled over the people's eyes, shedding light on the truth hidden therein, and enlightening the world. Never once is a single punch thrown, yet the oppressor is vanquished. Never once is retaliation used, yet justice is met. This is the kind of justice I want my children to know, this is the kind of conflict resolution I want the future to believe in. Children watch, follow in suit, and then understand. Always in that order. If we want them to have peace, we must practice it so they watch it. Watch it so they become it. Become it so they understand it. The future begins and ends with you, my dear readers and friends. Choose your actions wisely, for they shape the future more than we give them credit for.