I wanted to answer that, without getting super political in the Off Topic section.
First wave. Think end of the 19th and early 20th centuries.
Elizabeth Stanton, Sojourner Truth. Women’s suffrage. Basic rights of equality for women. Some of the earlier writers like philosopher John Stuart Mill (who I love), and Jane Austen (who I love) set the stage, but there were many earlier influences.
Second wave. Think 1960s to 1990s.
The era of the Equal Rights Amendment. National Organization for Women formed. Protests of the Miss America Pageant as promoting objectification of women. Abortion rights and the Pill give women more control over reproduction. Expansion of dual income families. Focus on pay male and female pay gaps. Some of this wave got tied into, or sometimes eclipsed by all the other things going on in our country during that time, including the Civil Rights Movement and the Vietnam War.
Third Wave. Think mid-1990s to present.
Note: It’s hard for me to try to be objective here because I don’t have a lot of use for the Third wave.
Post-modernist deconstruction of gender roles. Often sees ideas of sex and gender as too simplistic, or rejects them altogether. Celebration of ambiguity, and blurring gender lines. This is simplistic, but there’s some joining with LGBT agenda issues like the idea that there are no meaningful differences between males and females, but there are 52 distinct genders. Intersectional Feminism, which is a topic in itself. I have lots of problems with it.
Some young third wave feminists embracing symbols of female sexuality like high heels and make-up that the second wave feminists often rejected, while claiming derogatory names like “bitch”, “cunt”, and “slut” as symbols of female empowerment. The Slut Walk would fall under that category, and we had Kim Kardashian defending her nude selfies as a form of female empowerment, as a third wave feminist. Sure.
The idea that America is still every bit a patriarchy, but that the misogyny has only become more subtle, so we now become victimized and offended by smaller infractions and micro-aggressions.
We have long had more female graduates at every degree level, BS, MS, PhD, but the work won’t be done until we’re equally represented in STEM fields, and have equal numbers of women in every top level position, despite the fact that women continue to choose helping professions and humanities at higher rates. The controversial idea that we now have a campus rape culture where one-quarter of women are sexually assaulted. That’s a total garbage statistic, but third wave feminists love it and continue to quote it.
My opinion here. In it’s extremes, third wave feminists believe that male and females are in a zero sum war for power. Any differences between the sexes are seen as evidence of discrimination, rather than looking to other influences. For me, there’s a lack of respect for female choices like stepping away from work to raise kids, sex differences in major choice, a preference for part-time or flexible work.
There was a Pew poll in 2013 where mothers in the US were asked about their “ideal” working arrangement. Sixty-one percent said they would prefer to work part-time or not at all. IMO third wave feminists are out of touch with that reality, or interpret it as internalized female misogyny or of women wanting the wrong things.
About the zero sum war, men are our fathers, husbands, brothers and sons, so for families to flourish, we’re all better if both men and women are flourishing. In many ways, I think Third Wave feminists are a step backward from that. I don’t relate to it at all. Really.
For some humor. I like this quote. “No one will ever win the battle of the sexes. There’s too much fraternizing with the enemy.” - Henry Kissinger 
References - The Four Waves of Feminism by Martha Rampton,
and Christina Hoff Sommers, many articles. She’s a feminist who has a lot of problems with Third Wave ideas, and I generally agree with her. She’s not Conservative in any sense really, except she rejects a lot of the ideology of the third wave.