In the midst of stressful times, Jesus gave some encouraging truths to help the disciples, though there are still lingering questions. One of them is on how knowing Jesus means knowing the Father (14:7). We've seen Jesus talk about his link to the Father many times throughout John.
But then Philip had one comment. He wanted Jesus to show the Father directly. However, Jesus rhetorically asked Philip a few questions. He asked if Philip does not know Jesus after being with Jesus for so long (14:9). Jesus's point is that Philip has experienced the Father based on seeing what Jesus has done (especially since many of Jesus's actions reflect the heart of the Father).
Jesus later said that his own words are not "on [His] own authority" and that "the Father who dwells in [Him] does the works" (14:10). In other words, all of the words and deeds from Jesus are based on the Father. In fact, Jesus called Philip to believe that Jesus is in the Father and the Father is in Jesus or even just believe Jesus from his works (14:11). Many of Jesus's miracles (like water to wine and feeding 5000) involve the power of the Father.