Vox has a good explainer - here are some of the lowlights:

The budget resolution adopted by the US Senate last week, and by the House of Representatives on Thursday, is not a law. It cannot be signed or vetoed by the president, and the policies it recommends are just that -- recommendations.

But it still matters. The budget resolution changes the rules for passing certain legislation, especially in the Senate, and this resolution in particular will allow Republicans to pass $1.5 trillion in tax cuts (or more, depending on how they choose to do the math) over 10 years with only 51 votes.

[...]

The agenda the resolution outlines is radical. The federal welfare state would be rolled back in just about every dimension, with health care programs particularly affected. All non-Medicare health programs would see a cut of $1.3 trillion, or nearly 30 percent, by 2027, according to the Center on Budget and Policy Priorities.

Medicare would be cut too, to the tune of $473 billion. There is $1 trillion over 10 years in mystery cuts to mandatory programs, cuts that would in practice almost certainly hurt programs for the poor.

[...]

Also facing huge cuts, to the tune of $653 billion or 13 percent over 10 years (and 15.8 percent by 2027), is the "income security" spending category.

That includes a variety of major programs, most notably the Supplemental Nutrition Assistance Program (SNAP, or food stamps), Supplemental Security Income (SSI, an anti-poverty program that gives cash to seniors and disabled people), the earned income tax credit (EITC) for people too poor to pay taxes, unemployment insurance, and both military and civilian federal employee pensions.

There's more, and it's worth reading, if only because it makes starkly clear that this proposed budget gives the lie to all that hogwash the GOP is spewing about how much they care about the 99%.

Oh, and they're also looking at a ban on abortions later than 6 weeks.  Yes, by all means, more babies to deny health care, food and housing to just screams "we care about the people" doesn't it?

Several members of the House and Senate tax-writing committees said they were open to changes that could affect the rules for tax-advantaged retirement accounts used by tens of millions of Americans, such as 401(k)s and IRAs, or individual retirement accounts. But Trump and other Republicans have expressed reservations.

The House hasn't even released its tax reform bill yet, and Republican lawmakers are already making a big concession over one of their most controversial proposals.
Kevin Brady, chairman of the House Ways and Means Committee, has decided to only partially repeal the state and local tax deduction, bending to concerns of colleagues from high-tax states.