In string theory, strings are not typically considered as energy packages themselves. Instead, they are fundamental entities with length but no spatial extent in the traditional sense. Strings can vibrate and oscillate in different ways, and it is these vibrations that give rise to the different particles and their properties.
Strings do possess energy, but it is the vibrational modes of the string that determine the energy content. The different vibrational patterns of a string correspond to different particle states, such as photons, electrons, or quarks. The energy of a string is associated with the amplitude and frequency of its vibrations.
As for the idea that strings are made of the energy of the quantum vacuum or foam, it is an interesting concept but not a direct interpretation within string theory itself. The quantum vacuum, often referred to as the ground state of the quantum fields that permeate all of space, is a complex and dynamic entity governed by quantum mechanics. It is not explicitly described as the source of string formation or composition in the standard framework of string theory.
String theory, at its core, is based on the idea that fundamental particles are actually tiny vibrating strings, rather than point-like particles. The precise nature of the energy that sustains these strings and gives rise to their vibrational modes is still an active area of research within string theory. It involves understanding the dynamics and properties of strings within the framework of the theory and how they interact with the surrounding spacetime and other particles.
It's worth noting that the nature of the quantum vacuum and its relationship to string theory are areas of ongoing investigation, and our understanding of these concepts may continue to evolve as research progresses.