Here X = is the value of x axis and y= is the value of y axis
fill = is work like css's background-color mean to fill color on background
stroke define the object strock
stroke-width = for thickness of stroke.
stroke-opacity = stroke opacity
Circle have not height and width so height and width define is by,
r = Radius, cx and cy same as x and y
rx = for horizontal radius and ry = vertically radius
points = is depands on your shape its write like (points="0,90 10,140 90,120")
Its a path for triangle the and every point is show x and y axis distance (points="x,y x,y x,y")
and for line x1 and y1 are start point of their coordinates and x2,y2 are end points.
I think it's an important tag of SVG because you can make every type of shape using this
<path d="" stroke-width="" stroke="" fill=""/>
d= Its show the path direction
L = for start next direction, M = start point, H = horizontal lineto, V = vertical lineto, C = curveto, S = smooth curveto, Q = for quadraticurve
T = smooth quadratic Bzier curveto, A = ellipse arc, Z = end point