It is a symbol of the vast discrepancy in power between the Palestinian people and Israel's war machine.
Stones aimed at Israeli tanks or other armed vehicles were a means for the unarmed indigenous people of Palestine to demonstrate their refusal of occupation and oppression. Youth, women, the elderly and all sectors of society participated in this form of resistance.
Stones could be violent, however, when used systematically by Israeli soldiers to smash Palestinians' limbs, as part of a policy ordered by Yitzhak Rabin, then Israeli minister of defence, to "break their bones". The Knesset refused to even investigate Rabin's order, and he was never been held accountable.
Moreover, media outlets advocating for these nonviolent tactics have chosen to completely overlook the Boycott Divestment and Sanctions (BDS) movement against Israel. Although it does not fall under the two forms of resistance mentioned earlier, it can be only be categorised as a strictly non-violent tactic, aiming to pressure Israel to abide by its obligations under international law.
The overwhelming growth in the BDS movement, met with little to no coverage of its successes by most mainstream media outlets can only be an indicator of the hypocrisy of their coverage of Palestinian resistance: only shedding light on forms of resistance they categorise as relevant - or, dare I say, worthy.
Finally, it is important to comprehend the context of the Palestinian-Israeli conflict that is often called "complex". In fact, and at the risk of oversimplifying, it is a conflict between an oppressor and an oppressed. Within that context the use of violence and force can be exemplified perfectly in the words of Paulo Freire:
"Never in history has violence been initiated by the oppressed. How could they be the initiators, if they themselves are the result of violence? How could they be the sponsors of something whose objective inauguration called forth their existence as oppressed? There would be no oppressed had there been no prior situation of violence to establish their subjugation. Violence is initiated by those who oppress, who exploit, who fail to recognise others as persons - not by those who are oppressed, exploited and unrecognised."
in full:
http://english.aljazeera.net/indepth/opinion/2011/06/201162895553754742.html