Your progressed chart adds one day to your date of birth for every year you've been alive to create a new chart reflective of how you change with age. It can also be used in predictive astrology analysis. Your progressed Venus moves roughly 1 degree per year, and can show how who and what you love changes as you get older.
None of us love the same exact things and people our entire lives. Of course this evolves as we evolve. Our wants and needs in relationships and what we're willing to give evolves as well. This can be seen through your progressed Venus.
Changing With Progressed Venus
Your progressed Venus will change signs roughly 2-3 times in your life, and will move through 2-3 different natal houses. This shows the changes that you go through when it comes to what you need in relationships, what your relationships look like, who you attract, and your relationships overall.
Big changes can happen in relationships when your progressed Venus is getting ready to change signs. At 29 degrees, your Venus is anaretic, and this can be a time when you want to push for things in relationships before Venus changes signs. Once Venus goes into a new sign, you can feel a shift happening in your relationships. This can take a couple of years to adjust to.
It can be similar when your progressed Venus enters a new natal house, and you can see changes happening in your relationships then as well. You may experience major developments in your relationships when your progressed Venus is actually changing houses, generally up to a year before and after.
Your progressed Venus can also make aspects to your natal and progressed charts, and this can impact your relationships as well. These aspects can be strong but overarching since they last a couple of years (so they're more in line with transit Neptune or Pluto aspects).
It can be hugely significant when your progressed Venus turns retrograde or direct. This is a whole different approach to everything involving others and your relationships, and there can be super major developments around when this happens. The adjustment period may be longer with this.
Transits and your Progressed Venus
You can track transit aspects to your natal planets, and you can also track transit aspects to your progressed planets, including your progressed Venus. Since your progressed Venus is ahead of your natal Venus (usually, unless retrograde), this can expand aspects by transit planets as they first hit your natal Venus and then hit your progressed Venus some time later. Might be many years later!
And in some cases, transit aspects to your progressed Venus can last for many years. Progressed Venus and transit Pluto, for example, can move together for 10 or more years if they sync up right. This can be very helpful when it's a beneficial aspect (sextile or trine), but pretty challenging when it's a conjunction, square, or opposition (can sometimes explain reeeeeally long periods alone!).
Synastry involving Progressed Venus
You can use your progressed Venus when looking at whether or not you connect with someone, similarly to your natal Venus. This difference is that your progressed Venus is temporary while your natal Venus is permanent. That means connections that occur to your progressed Venus may not stick around once your progressed Venus has moved on, unless you have other natal chart and composite chart connections to make it last. It can be strong while it's in effect, but it needs something else to keep it.
Suggested Reading: The articles in the Love Astrology Series for Mars, Jupiter, Saturn, Uranus, Neptune, Pluto, the 12th house, Chiron, eclipses, retrogrades, the Asteroids of Your Name, and the Lunar Nodes