A PNG is a raster image: a grid of coloured pixels with an optional transparent background. An EPS (Encapsulated PostScript) is a print format that describes a drawing with PostScript commands, and it can hold either vector shapes or a plain bitmap. That second option is the catch. Many PNG to EPS converters simply wrap your pixels in an EPS file; the extension changes, but the picture is still pixels and still goes soft or blocky when it is printed large.
To get a vector EPS, the image has to be traced: every edge is found and redrawn as smooth curves and straight lines, and every colour area becomes a filled shape. We do that with an AI vectorizer built for logos and graphics, then write the shapes into a standard EPSF 3.0 file with RGB colours, so what you download is resolution-independent artwork rather than a renamed picture.
PNG to EPS tracing is an interpretation of the image, not a lossless copy. Clean logos, icons, badges and flat illustrations come out almost identical to the original; photos with soft gradients become many small colour patches. The free watermarked preview shows you exactly which case you are in before you spend a credit.