user10246: I have read the wiki page and I would like some further and more technical(if possible) confirmation for a few things. 
A bitcoin node is a user which is connected to the network through a client. This node can perform transactions, try to build a block inside a mining pool, or just exist in the network. Are there any further actions for a node?
If a node exists inside the network how can he verify the transactions?
Furthermore is there a paper or something that explains things in a lower level of how exactly the system works in case of transactions and mining? I do not want a description but something more technical.

user85: 
A bitcoin node is a user which is connected to the network through a client. This node can perform transactions, try to build a block inside a mining pool, or just exist in the network. Are there any further actions for a node?

Nodes also relay blocks and transactions to other nodes. They also validate incoming blocks and transactions and keep track of the current, longest valid blockchain. That's pretty much it.

If a node exists inside the network how can he verify the transactions?

There are a set of mathematical rules that determine if transactions are valid. The nodes check the transactions against those rules. If they meet the rules, they are valid.

Furthermore is there a paper or something that explains things in a lower level of how exactly the system works in case of transactions and mining? I do not want a description but something more technical.

Almost every question you can think of is answered, in technical detail, somewhere in the Bitcoin wiki.

10246: <p>I have read the wiki page and I would like some further and more technical(if possible) confirmation for a few things. 
A bitcoin node is a user which is connected to the network through a client. This node can perform transactions, try to build a block inside a mining pool, or just exist in the network. Are there any further actions for a node?
If a node exists inside the network how can he verify the transactions?
Furthermore is there a paper or something that explains things in a lower level of how exactly the system works in case of transactions and mining? I do not want a description but something more technical.</p>
 85: <blockquote>
  <p>A bitcoin node is a user which is connected to the network through a client. This node can perform transactions, try to build a block inside a mining pool, or just exist in the network. Are there any further actions for a node?</p>
</blockquote>

<p>Nodes also relay blocks and transactions to other nodes. They also validate incoming blocks and transactions and keep track of the current, longest valid blockchain. That's pretty much it.</p>

<blockquote>
  <p>If a node exists inside the network how can he verify the transactions?</p>
</blockquote>

<p>There are a set of mathematical rules that determine if transactions are valid. The nodes check the transactions against those rules. If they meet the rules, they are valid.</p>

<blockquote>
  <p>Furthermore is there a paper or something that explains things in a lower level of how exactly the system works in case of transactions and mining? I do not want a description but something more technical.</p>
</blockquote>

<p>Almost every question you can think of is answered, in technical detail, somewhere in the <a href="https://en.bitcoin.it/wiki/Main_Page" rel="nofollow">Bitcoin wiki</a>.</p>
